Depends on the condition of the barrel for me ... 99% of my rifles are Military so some need a different method than others depending. The basic pattern ...
# - Short Scrub is a multi use cleaner I use ... you can leave in the bore indefinitely and it will keep on working without damage or etching.
1 - Wet patch or bore mop ( I use either )
2 - Push patch/mop through
3 - Stand rifles upright on paper so solvent runs away from chamber and leave overnight ...
4 - Day 2 ... patch out until clean.
5 - If still dirty, hit with bronze brush, 10 passes
6 - Leave over night ... repeat until clean.
7 - When done, run oil on patch through bore and put to bed.
No mystery ... just patience and time/effort.